电极电势调控对氨氧化脱氮与生物膜电活性的影响

Effects of electrode potential regulation on ammonium oxidation denitrification and electroactivity of biofilms

为解决低C/N值含氮废水在处理过程中碱度和碳源不足的问题,通过电极电势调控的方式干预氨氧化脱氮及生物膜电化学活性.在处理碱度不足(1.0 g/L NaHCO3)的低C/N含氮废水时,外加正电势+0.3、+0.4、+0.6 V(vs Ag/AgCl),系统氨氧化率分别为54.59%、59.31%、37.97%,相较于不加电势体系(70.79%),最大降低了46.24%;外加负电势-0.6、-0.8、-1.0 V(vs Ag/AgCl)时,氨氧化率分别为93.41%、79.27%、83.23%,相较于不加电势时最大提高了31.95%;但总氮去除率在正负电势条件下均有提高,与对照组(9.38%)相比,最高总氮去除率为23.47%,达对照组的2.5倍.CV扫描结果显示,外加电势后工作电极生物膜在-0.25V至-0.35V范围出现还原峰,对照组无明显峰出现,且电流相较对照组更大,对比说明外加电势能够调控生物膜的电化学活性.16S rRNA分析发现,对比未加电势,外加电极电势后电极生物膜中的放线菌门相对丰度减少,变形菌门和绿弯菌门相对丰度增加,Nitrosomonas sp.、Nitrosospira sp.、Bradyrhizobiaceae sp.及Rhodanobacter sp.等具有氨氧化和反硝化作用的菌属被同步富集.本研究基于脱氮菌组成及其电化学活性,推测存在硝化/反硝化氮素转化的直接种间电子传递(DIET)途径,促进了低C/N值废水脱氮.(图6参31)

To solve the problem of insufficient alkalinity and carbon source in the treatment of nitrogenous wastewater with a low C/N ratio, the electrode potential is set to regulate ammonia oxidation and the electrochemical activity of biofilm for nitrogen removal. With a positive potential of +0.3 V, +0.4 V, and +0.6 V(vs. Ag/AgCl) applied to the working electrode with 1.0 g/L NaHCO3, the removal efficiencies of ammonia decrease to 54.59%, 59.31%, and 37.97%, respectively, with the maximum decrease to 46.24% of the control group without applying a potential(70.79%). While, with the negative potentials of-0.6 V,-0.8 V, and-1.0 V(vs. Ag/AgCl), the removal efficiencies of ammonia increase to 93.41%, 79.27%, and 83.23%, respectively, with the maximum increase to 31.95% compared with the control group without applying a potential. However, the removal efficiency of total nitrogen is improved under both positive and negative potential conditions. The total nitrogen removal efficiency in the control experiment was only 9.38%, while the highest removal efficiencies of the negative potential group rose to 23.47%, which was 2.5 times as much as the control. Moreover, the cyclic voltammetry analysis results showed that the working electrode biofilm had a reduction peak in the range of-0.25 V to-0.35 V after applied potential. However, there was no obvious peak in the control experiment, and the current was larger than in the control group, indicating that applying potential could regulate the electrochemical activity of the biofilm. According to 16S rRNA analysis, the relative abundance of the Actinomycete phylum decreased in the group with applied potential compared with the control group. However, the phyla of Proteobacteria and Chloroforms increased, and the dominant bacteria such as Nitrosomonas sp., Nitrosospira sp., Bradyrhizobiaceae sp., and Rhodanobacter sp. with ammonia oxidation and denitrification activities were simultaneously enriched. Based on the microbial community and electrochemical activity of denitrification bacteria, it is speculated that there is a direct interspecific electron transfer(DIET) pathway for nitrogen conversion in the nitrification/denitrification process, which improves nitrogen removal in ammoniacontaining wastewater with a low C/N ratio.